Helicopter rotors



FIG. 1 is a side elevation view of helicopter rotors, showing our new design;

FIG. 2 is an elevation of the side opposite that shown in FIG. 1;

FIG. 3 is a top perspective view thereof; and,

FIG. 4 is a top perspective view thereof.

Broken lines are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for helicopter rotors, as shown and described. 